/*
 * Downsampling (64-bit MMI)
 *
 * Copyright (C) 2015, 2018-2019, 2025-2026, D. R. Commander.
 * Copyright (C) 2016-2017, Loongson Technology Corporation Limited, BeiJing.
 * Authors:  ZhuChen     <zhuchen@loongson.cn>
 *           CaiWanwei   <caiwanwei@loongson.cn>
 *           SunZhangzhi <sunzhangzhi-cq@loongson.cn>
 *
 * Based on the x86 SIMD extension for IJG JPEG library
 * Copyright (C) 1999-2006, MIYASAKA Masaru.
 *
 * This software is provided 'as-is', without any express or implied
 * warranty.  In no event will the authors be held liable for any damages
 * arising from the use of this software.
 *
 * Permission is granted to anyone to use this software for any purpose,
 * including commercial applications, and to alter it and redistribute it
 * freely, subject to the following restrictions:
 *
 * 1. The origin of this software must not be misrepresented; you must not
 *    claim that you wrote the original software. If you use this software
 *    in a product, an acknowledgment in the product documentation would be
 *    appreciated but is not required.
 * 2. Altered source versions must be plainly marked as such, and must not be
 *    misrepresented as being the original software.
 * 3. This notice may not be removed or altered from any source distribution.
 */

#include "jsimd_mmi.h"
#include "../common/jcsample.h"


HIDDEN void
jsimd_h2v2_downsample_mmi(JDIMENSION image_width, int max_v_samp_factor,
                          JDIMENSION v_samp_factor, JDIMENSION width_in_blocks,
                          JSAMPARRAY input_data, JSAMPARRAY output_data)
{
  int inrow, outrow, outcol;
  JDIMENSION output_cols = width_in_blocks * DCTSIZE;
  JSAMPROW inptr0, inptr1, outptr;
  __m64 bias, mask = 0.0, thisavg, nextavg, avg;
  __m64 this0o, this0e, this0, this0sum, next0o, next0e, next0, next0sum;
  __m64 this1o, this1e, this1, this1sum, next1o, next1e, next1, next1sum;

  expand_right_edge(input_data, max_v_samp_factor, image_width,
                    output_cols * 2);

  bias = _mm_set1_pi32((1 << 17) + 1);   /* 0x00020001 (32-bit bias pattern) */
                                         /* bias = { 1, 2, 1, 2 } (16-bit) */
  mask = _mm_cmpeq_pi16(mask, mask);
  mask = _mm_srli_pi16(mask, BYTE_BIT);  /* { 0xFF 0x00 0xFF 0x00 .. } */

  for (inrow = 0, outrow = 0; outrow < v_samp_factor;
       inrow += 2, outrow++) {

    inptr0 = input_data[inrow];
    inptr1 = input_data[inrow + 1];
    outptr = output_data[outrow];

    for (outcol = output_cols; outcol > 0;
         outcol -= 8, inptr0 += 16, inptr1 += 16, outptr += 8) {

      this0 = _mm_load_si64((__m64 *)&inptr0[0]);
      this1 = _mm_load_si64((__m64 *)&inptr1[0]);
      next0 = _mm_load_si64((__m64 *)&inptr0[8]);
      next1 = _mm_load_si64((__m64 *)&inptr1[8]);

      this0o = _mm_and_si64(this0, mask);
      this0e = _mm_srli_pi16(this0, BYTE_BIT);
      this1o = _mm_and_si64(this1, mask);
      this1e = _mm_srli_pi16(this1, BYTE_BIT);
      this0sum = _mm_add_pi16(this0o, this0e);
      this1sum = _mm_add_pi16(this1o, this1e);

      next0o = _mm_and_si64(next0, mask);
      next0e = _mm_srli_pi16(next0, BYTE_BIT);
      next1o = _mm_and_si64(next1, mask);
      next1e = _mm_srli_pi16(next1, BYTE_BIT);
      next0sum = _mm_add_pi16(next0o, next0e);
      next1sum = _mm_add_pi16(next1o, next1e);

      thisavg = _mm_add_pi16(this0sum, this1sum);
      nextavg = _mm_add_pi16(next0sum, next1sum);
      thisavg = _mm_add_pi16(thisavg, bias);
      nextavg = _mm_add_pi16(nextavg, bias);
      thisavg = _mm_srli_pi16(thisavg, 2);
      nextavg = _mm_srli_pi16(nextavg, 2);

      avg = _mm_packs_pu16(thisavg, nextavg);

      _mm_store_si64((__m64 *)&outptr[0], avg);
    }
  }
}
